As shown in Fig. 4, a hair clip of the prior art comprises a movable cover 3 provided at one end thereof with an arcuate retainer 31 having a bottom end which is provided with an inverted hook 32 engageable with a retaining portion 34 of a base 33 of the hair clip. When the hook 32 is engaged with the retaining portion 34 of the base 33, the bottom end of the arcuate retainer 31 is jutted out from the end of the base 33.
Such a prior art hair clip as described above is defective in design in that the jutted arcuate retainer 31 is rather vulnerable to being disturbed by an external force to bring about the disengagement of the hook 32 with the retaining portion 32 of the base 33.